As far as I can tell, this isn't a new bug in as much as InDesign CS3, CS4, CS5 and CS5.5 (Mac) all exhibit the same problem exporting soft-returns in Unicode encoded Tagged Text where they are replaced with hard returns on import. Unfortunately it appears that we may be the only ones that care and thus it's unlikely that Adobe will fix it (unless someone adopts it as a JDI bug).

Update: after testing some more it appears this is an export bug for Mac OS-only. In other words, if you use a PC to export a story that contains soft-returns to Tagged Text (Unicode), the soft-returns are preserved when placing into a document using a Mac. And vice-versa, using a Mac to export a story with soft-returns to Tagged Text (Unicode) and then placing this into a document using a PC exhibits the same substitition of soft-returns for hard-returns.

I don't know if this will help you, but when I write a Unicode tagged text file with soft returns (unix LF aka ASCII 10) out of Filemaker on an Intel Mac OS X 10.5, it imports correctly into InD CS4. Filemaker writes a UTF16 file and InD needs UTF16, so that may have some bearing on the problem. When I open the tagged text file with TextWrangler and select the soft return, the character shows as a unix LF as expected.

When I tried simply exporting a story and importing it back using InD CS4 only, I did get the same error as you describe.

Yep, it's just a deficiency with InDesign's export to Unicode tagged text, not with the import. So as long as we don't trust InDesign (Mac) to "do the right thing" with its own tagged text export… we'll be fine.

that very interesting that at import time with a Mac this "soft-return" will import correctly when the file ist unicode encoded. Can you open this "good" file wich a Hexeditor and post which unicode code is used for the softreturn. Or better post a link to a downloadable file which will import fine. I've never found an answer to this problem an I' searching since CS3 :-(